It is well-known in the art to use microwave phasing structures, commonly referred to as reflectarray elements or dipole elements, for electromagnetically emulating shaped reflective surfaces. The emulation occurs by controlling the reflection phases of the dipole elements that are positioned on the reflective surface. The reflection phases of the dipole elements are controlled by varying, among other things, the size, shape, length, and width of the reflectarray elements. These variations in the dipole elements modify the elemental reactance and thereby induce a reflection phase shift. Ideally, the larger the phase range of the reflectarray, the more signals it will be able to process through transmission and receipt. Currently, however, in order to increase the phase dynamic range for a reflectarray antenna, the bandwidth performance of the antenna will correspondingly decrease.
One known way of phasing dipole elements for linear polarization is to provide a plurality of parallel dipole elements across the surface of the reflectarray. The elements are typically arranged in a matrix with dipole elements extending across the reflectarray surface in rows and columns. In order to change the phase of a particular dipole element, the length or width of the dipole element is typically varied. Thus, the dipole elements in the matrix can vary in length and width from one dipole element to another. However, the length and width that the dipoles can be effectively varied is limited. For example, the length that a dipole element can be increased is limited due to interference with corresponding dipole elements in adjacent rows. Similarly, the width of a dipole element is limited because if it is made too thin, it can tear thus rendering it inoperable.
Accordingly, the configuration of these prior phasing dipole elements is disadvantageous in that they do not allow the phase dynamic range available from a reflectarray element to achieve a full 360 degrees without negatively impacting bandwidth performance. Attempts to increase the dynamic range of the prior art dipole elements have resulted in decreased bandwidth performance. Conversely, when the dipole elements are arranged in an attempt to provide better bandwidth performance, the phase dynamic range of the reflectarray elements decreases. Accordingly, there is no known way to provide both optimum dynamic phase range and optimum bandwidth performance.